Hierarchical, adaptive cache consistency in a page server OODBMS

Due to its simplicity and communication efficiency, many client-server object-oriented database systems are based on the basic page server architecture-pages serve as their smallest unit of data transfer, client caching, and concurrency control. In an earlier paper, we showed how to extend this architecture to permit object-level callback locking, and we showed through simulations that significant performance gains can be expected. In the current paper, we report on our experiences from implementing this approach in the context of the SHORE system. Since SHORE supports multiple lock granularities (volume, file, page, object), we explain how our callback algorithm can be extended to support multigranularity locking. We also discuss some of the stickier issues that arose as we moved our algorithm out of the simulator and into SHORE, which supports a generalized peer-servers architecture. Finally, we present performance measurements that explore the tradeoffs between page-level and object-level concurrency control. Our measurements were obtained by running SHORE on an IBM SP2 shared-nothing parallel machine.